Naturally occurring substances from nudibranchs (marine mollusks) will be purified, chemically identified and studied pharmacologically. The principle substance so far identified is a methyl nucleoside from the digestive glands of Anisodoris nobilis. It produces prolonged hypotension and bradycardia in mammals. The work will include proof of structure by synthesis and/or X-ray crystallography; detailed study of the mechanism of hypotension in mammals; and study of the mechanism of negative inotropic and chronotropic effects on isolated hearts.